1. Field of the Invention
The present invention relates to an improvement of a slitter for steel belt consisting of steel cords and topping rubber. As being well known, a steel belt has been usually employed as a constituent of an automobile tire. The present invention intends to improve the slitter so as to obtain a steel belt having uniform width throughout the full length.
2. Prior Art
A steel belt employed as a constituent of a radial tire whose width is comparatively narrow is usually provided by the following steps in the prior art. A belt material consisting of steel cords and topping rubber is first cut into a plurality of segments having a comparatively wide width by a bias-cutter. Next, said segments are connected with each other in the longitudinal direction to be rolled as a wider belt material and subsequently said wider belt material is slitted into a steel belt of the desired width by rotary blades installed at a slitter and comprising an upper blade and a lower blade having the circumferential portions slightly overlapped and contacting each other. However, since steel cords are arranged at a small angle with respect to the longitudinal direction of the belt material, a strong force which thrusts steel cords in the transverse direction occurs when the belt material is slitted by rotary blades in the longitudinal direction so that the belt material moves in the transverse direction. Consequently, it is inevitable that the width of the steel belts obtained is not uniform.
Furthermore, since steel cords are arranged at a small angle with respect to the longitudinal direction and have a high elasticity, the belt material is twisted at a freely suspended curved portion formed between a delivering device of the belt material and a slitter, so that the belt material is apt to be delivered not in alignment with the rotary blades. The uniformity of a steel belt is also injured by this inaccurate delivery of the belt material. There have been adopted such countermeasures as making the radius of curvature of a lead-in guide larger which is provided at a slitter for leading the belt material toward rotary blades, and as installing upright guide rollers at each side of the lead-in guide in the direction of movement of the belt material. The results obtained, however, are not satisfactory.
Even a slight off-set of a steel belt relative to the equatorial line of a radial tire badly affects the uniformity of a radial tire, so that it is very important to make the width of a steel belt uniform. Therefore, it is earnestly demanded to improve the accuracy of slitting by a slitter as well as the accuracy of cutting by a bias-cutter.